Process for the preparation of a catalyst based on molybdenum for use in hydrotreatment or in hydrocracking

ABSTRACT

The invention concerns a process for the preparation of a catalyst for carrying out hydrogenation reactions in hydrotreatment and hydrocracking processes. Said catalyst is prepared from at least one mononuclear precursor based on molybdenum (Mo), in its monomeric or dimeric form, having at least one Mo═O or Mo—OR bond or at least one Mo═S or Mo—SR bond where [R═C x H y  where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR′) 3  or R═Si(R′) 3  where R′═C x′ H y′  where x′≧1 and (x′−1)≦y′≦(2x′+1)], and optionally from at least one promoter element from group VIII. Said precursors are deposited onto an oxide support which is suitable for the process in which it is used, said catalyst being dried at a temperature of less than 200° C. then advantageously being sulphurized before being deployed in said process.

FIELD OF THE INVENTION

The present invention describes a process for the preparation of acatalyst based on molybdenum (Mo) which is particularly effective in thehydrogenation reactions involved in hydrotreatment and hydrocrackingprocesses, as well as in the hydrocracking reactions proper involved inhydrocracking processes.

The present invention also relates to the use of said catalyst inhydrotreatment and/or hydrocracking processes.

PRIOR ART General Remarks on Catalysts for the Hydrotreatment (HDT) andHydrocracking (HCK) of Hydrocarbon Feeds

The composition and use of catalysts for the hydrotreatment andhydrocracking of hydrocarbon feeds have been fully described in thefollowing works respectively: “Catalysis by transition metal sulphides,From Molecular Theory to Industrial Application”, 2013,

H. Toulhouat, P. Raybaud, and “Hydrocracking Science and Technology”,1996, J. Scherzer, A. J. Gruia, Marcel Dekker Inc.

Thus, catalysts used in refining processes, whether intended forhydrotreatment or hydrocracking reactions, are generally characterizedby a hydrodehydrogenating function supplied by the presence of an activephase based on at least one metal from group VIB and optionally at leastone metal from group VIII of the periodic classification of theelements. The most common formulations are of the cobalt-molybdenum(CoMo), nickel-molybdenum (NiMo) and nickel-tungsten (NiW) type. Thesecatalysts may be in the bulk form (of specific value for hydrotreatmentcatalysts) or indeed in the supported state, which in this case employsa porous solid of a different nature. In this latter case, the poroussupport is generally an amorphous or low crystallinity oxide (alumina,aluminosilicate, etc), optionally associated with a zeolitic ornon-zeolitic material. After preparation, at least one metal from groupVIB and optionally at least one metal from group VIII constituting saidcatalysts are often present in an oxidized form. Since the active andstable form for hydrocracking processes (HCK) and hydrotreatment (HDT)processes is the sulphurized form, these catalysts have to undergo asulphurization step. This may be carried out in a unit associated withthe process (referred to as in situ sulphurization) or prior to chargingthe catalyst into the unit (referred to as ex situ sulphurization).

The skilled person is generally aware that good catalytic performancesin the fields of application mentioned above are a function of: 1) thenature of the hydrocarbon feed to be treated, 2) the process employed,3) the operating conditions for the function which is selected, and 4)the catalyst used. In the latter case, it is also known that a catalystwith a high catalytic potential is characterized by: 1) an optimizedhydrodehydrogenating function (associated active phase ideally dispersedat the surface of the support and having a high active phase content)and 2) in the particular case of processes employing HCK reactions, by agood equilibrium between said hydrodehydrogenating function and thecracking function. It should also be noted that ideally, irrespective ofthe nature of the hydrocarbon feed to be treated, the active sites ofthe catalyst have to be accessible to the reagents and reaction productswhile developing a high active surface area, which could lead tospecific constraints in terms of structure and texture of theconstituent oxide support for said catalysts.

The usual methods leading to the formation of the hydrodehydrogenatingphase of the hydrotreatment and hydrocracking catalysts consist ofdepositing precursor(s) comprising at least one metal from group VIB andoptionally at least one metal from group VIII onto an oxide supportusing a “dry impregnation” technique, followed by steps for maturing,drying and optionally calcining, resulting in the formation of the oxideform of said metal(s) employed. Next comes the final step ofsulphurization, generating the active hydrodehydrogenating phase asmentioned above.

The catalytic performances of catalysts obtained from those“conventional” synthesis protocols have been studied extensively. Inparticular, it has been shown that for relatively high metal contents,phases are formed which are refractory to sulphurization consecutive tothe calcining step (sintering phenomenon) (H. Toulhouat, P. Raybaud“Catalysis by transition metal sulphides, From Molecular Theory toIndustrial Application”, 2013). As an example, in the case of catalystsof the CoMo or NiMo type supported on a support of alumina nature, theseare 1) crystallites of MoO₃, NiO, CoO, CoMoO₄ or Co₃O₄, of a dimensionsufficient to be detected by XRD, and/or 2) species of the typeAl₂(MoO₄)₃, CoAl₂O₄ or NiAl₂O₄. The three species cited above,containing the element aluminium, are well known to the skilled person.They result from interaction between the alumina support and theprecursor salts in solution of the active hydrodehydrogenating phase,which specifically results in a reaction between the Al³⁺ ions extractedfrom the alumina matrix and said salts in order to form Andersonheteropolyanions with formula [Al(OH)₆Mo₆O₁₈]³⁻, which are themselvesprecursors for the phases which are refractory to sulphurization. Thepresence of this set of species leads to an indirect non-negligible lossof catalytic activity of the associated catalyst as the entirety of theelements belonging to at least one metal from group VIB and optionallyat least one metal from group VIII is not used to its maximum potential,since a portion thereof is immobilized in inactive or low activityspecies.

The catalytic performances of the conventional catalysts described abovecould thus be improved, in particular by developing novel methods forthe preparation of such catalysts which could:

1) ensure good dispersion of the hydrodehydrogenating phase, inparticular for high metal contents (for example by controlling the sizeof the particles based on transition metals, maintaining the propertiesof these particles after heat treatment before sulphurization, etc.),2) limiting the formation of species refractory to sulphurization, forexample by better control of the interactions between the activehydrodehydrogenating phase (and/or its precursors) and the poroussupport employed, or by obtaining a better synergy between thetransition metals constituting the active phase, etc.;3) ensuring good diffusion of the reagents and the reaction productswhile maintaining the high developed active surface areas (optimizingthe chemical, textural and structural properties of the porous support).

The NiMo pairing is recognized as being the pairing of metals fromgroups VIB and VIII which is optimal for the hydrogenation of aromaticsand also for hydrodenitrogenation, which are key functions inhydrotreatment reactions or for hydrocracking. Despite the largequantities of NiMo deposited on the support by the “conventional” routeusing the usual precursors (H₃PO₄, MoO₃ Ni(OH)₂ or ammoniumheptamolybdate and nickel nitrate), and despite the parametric studiesconcerning the preparation steps, we have not been able to 1) controlthe dispersion and morphology of the sheets, and 2) optimize the degreeof promotion of the active phase generated on the supports: these arekey essentials in substantially reinforcing the hydrogenating power ofthe active phase and thus of carrying out the desired hydrogenationreactions in the hydrotreatment processes and/or of increasing the yieldof middle distillates in the hydrocracking process. One of thescientific challenges of recent years has been to optimize thehydrogenating phase deposited on the various supports for catalystsintended for hydrotreatment and hydrocracking.

Thus, it is clearly advantageous to discover means for preparinghydrotreatment catalysts which can be used to obtain novel catalystswith improved performances. The prior art shows that researchers haveturned to a variety of methods, including using many and variouspolyoxometallates, adding doping elements, adding organic molecules withmany and various properties (solvation, complexing, etc) or finally, butto a lesser extent because of difficulties in use, using mononuclearprecursors.

Preparation of Hydrotreatment and Hydrocracking Catalysts fromPolyoxometallates (POM)

The advantage of polyoxometallates has already been mentioned in theprior art. As an example, document U.S. Pat. No. 2,547,380 mentions thebeneficial use of heteropolyacid salts of metals from group VIII such ascobalt or nickel salts of phosphomolybdic acid or silicomolybdic acid.In that patent, the heteropolyacid still contains phosphorus or silicon,this latter element being the central atom of the structure. Suchcompounds have the disadvantage of producing atomic ratios (element fromgroup VIII/element from group VI) which are limited. By way of example,cobalt phosphomolybdate has a Co/Mo ratio of 0.125.

Patent FR 2 749 778 describes the advantage of heteropolyanions withgeneral formula M_(x)AB₁₂O₄, in which M is cobalt or nickel, A isphosphorus, silicon or boron and B is molybdenum or tungsten; x takesthe value 2 or more if A is phosphorus, 2.5 or more if A is silicon and3 or more if A is boron. These structures have the advantage over thestructures disclosed in document U.S. Pat. No. 2,547,380 of obtainingatomic ratios (element from group VIII/element from group VI) which arehigher and thus produce better performing catalysts. This increase inthe ratio is obtained by means of the presence of at least a portion ofthe molybdenum or tungsten with a valency which is lower than its normalvalue of six, as appears in the composition of phosphomolybdic,phosphotungstic, silicomolybdic or silicotungstic acid, for example.

Patent FR 2 764 211 describes the synthesis and use of heteropolyanionswith formula M_(x)AB₁₁0₄₀M′C_((Z−2x)) in which M is cobalt or nickel, Ais phosphorus, silicon or boron and B is molybdenum or tungsten, M′ iscobalt, iron, nickel, copper or zinc, and C is a H⁺ ion or analkylammonium cation, x takes the value of 0 to 4.5, z a value between 7and 9. Thus, this formula corresponds to that claimed in the inventionFR 2 749 778, but in which one M′ atom is substituted with a B atom.This latter formula has the advantage of producing atomic ratios betweenthe element from group VIII and from group VIB which may be up to 0.5,and thus better promoted active phases.

Patent FR 2 315 721 demonstrates the advantage of usingheteropolycompounds with formula Ni_(x+y/2)AW_(11−y)O_(39−5/2y). H₂O andmore particularly the use of heteropolycompounds with formulaNi₄SiW₁₁O₃₉ and formula Ni₅SiW₉O₃₄, leading to unexpected catalyticperformances during hydrocracking and hydrotreatment.

In all of the cases, by using heteropolymolybdates orheteropolytungstate nickel salts, the teams researched encouraging themetal-promoter interaction by placing them in the same molecular entity,which means that the degree of promotion of the sulphurized catalyst canbe controlled and thus the number of active sites can be increased.

Finally, the use of these polyoxometallates trapped in mesostructuredsilicas has also been revealed in patents FR 2 969 647 and FR 2 969 645.The catalysts of the invention have exhibited highly interestingperformances in gas oil hydrotreatment and hydrocracking compared withcatalysts prepared in a conventional manner (impregnation ofpolyoxometallates onto mesoporous supports).

Preparation of Hydrotreatment or Hydrocracking Catalysts by AddingOrganic Molecules

Adding an organic compound to hydrotreatment catalysts in order toimprove their activity is now well known to the skilled person. A numberof patents protect the use of various ranges of organic compounds suchas mono, di- or polyalcohols which can optionally be etherified (WO96/41848, WO 01/76741, U.S. Pat. No. 4,012,340, U.S. Pat. No. 3,954,673,EP 0 601 722). Catalysts modified with C₂-C₁₄ monoesters are describedin patent applications EP 0 466 568 and EP 1 046 424, but suchmodifications do not always increase the performance of the catalystsufficiently for it to comply with specifications concerning the sulphurcontents of fuels which are constantly being made more restrictive forthe refiners.

In order to overcome this, patent FR 2 880 823 describes the use of acatalyst comprising metals from group VIB and VIII, a refractory oxideas the support, and an organic compound comprising at least 2 estercarboxylic functions with formula R1-O—CO—R2-CO—O—R1 orR1-CO—O—R2-O—CO—R1, or indeed C₁-C₄ dialkyl succinate with acetic acidin patent FR 2 953 740.

Other patents in the prior art describe a gain in activity linked to thecombined use of an organic acid or an alcohol on a hydrotreatmentcatalyst, as described in the patent application published under numberJP1995-136523 by KK Japan Energy, or linked to the use of a cyclicoligosaccharide, as in U.S. Pat. No. 2,963,360, for example.

Even though the gains in activity are sometimes poorly explained, theinterest in using organic molecules during the preparation ofhydrotreatment and hydrocracking catalysts no longer has to bedemonstrated, but such preparations are still limited by the number ofsteps and by the organic molecules to be impregnated being insoluble inthe aqueous solutions which are normally used.

Preparation of Hydrotreatment and Hydrocracking Catalysts UsingMononuclear Precursors (Precursor Containing Only One Metal Atom in itsStructure)

Preparations concerning supported catalysts starting from differentpolyoxometallate precursors having only a single molybdenum or tungstenatom in their structure have been known for a long time but are stillrare.

Since the 1980s, it has been shown that the use of organometallicprecursors based on Mo or W of the allyl type (WR₄ where R═C₄H₇)deposited on SiO₂ can be used to generate NiW or NiMo catalysts theintrinsic activities of which (activity with respect to Mo or W atom) inhydrodesulphurization are up to 4 times higher than those of catalystsprepared in a more conventional manner (use of ammonium heptamolybdate(NH₄)₆Mo₇O₂₄. 6H₂O in the case of catalysts prepared from Mo or tungsticacid, H₂WO₄ in the case of catalysts prepared from W) (Yermakov et al.,Journal of Molecular Catalysis, 1981, 205-214, Yermakov, Journal ofMolecular Catalysis, 21, 1983, 35-55 and Yermakov et al., AppliedCatalysis 11, 1984, 1-13). However, catalysts prepared on silica fromorganometallic precursors are still more active (activity with respectto Mo or W atom) than catalysts prepared on alumina.

In the 1990s, CoMo on alumina type catalysts were prepared fromthiomolybdate (bis(tetrabutylammonium)tetrathiomolybdate (TBA)₂MoS₄)salts and the importance of using them was demonstrated forhydrodesulphurization applications (Halbert et al. Journal of Catalysis130, 1991, 116-129).

In 2008, the advantage of using molybdenum dioxodiacetylacetonate on anorganized mesoporous alumina was demonstrated for the preparation ofhydrotreatment catalysts (Kaluza et al., Applied Catalysis A: General,351, 2008, 93-101). These studies then showed that the CoMo and NiMocatalysts prepared from this precursor were more hydrodesulphurizingthan commercial catalysts. Patent EP 0 178 711 describes the preparationof hydrotreatment catalysts on silica starting from solutions containingMo halides, preferably MoCl₅, in the presence of nickel and/or cobalthalide, preferably nickel chloride and/or cobalt chloride hexahydrate,NiCl₂(H₂O)₆ and CoCl₂(H₂O)₆ respectively, in a nitrile type solvent,with optionally a chlorinated solvent in addition.

U.S. Pat. No. 5,137,859 describes the preparation of catalysts used forthe hydrodesulphurization of hydrocarbon oil cuts on an alumina supportstarting from a compound selected from alkoxides or chelating compoundsor molybdenum or chromium glycoxides and a compound selected fromalkoxides or chelating compounds or nickel or cobalt glycoxidesdissolved in an organic solvent selected from alcohols, ethers, ketonesand aromatic compounds. The freshly impregnated oxide catalyst then hasto undergo a step for drying at a temperature of approximately 150° C.in the presence or absence of oxygen and necessarily a step forcalcining at a temperature of at least 200° C. in an atmospherecontaining oxygen. Such treatments may encourage denaturing ofprecursors grafted by calcining the carbon-containing portion andpossibly generate polycondensation of the alkoxide species, either dueto the water present in the heat treatment gas or due to the water whichwould be liberated during calcining of the carbonaceous groups. Thus, itcan be assumed that the dispersion initially supplied during grafting ofthe intact species is lost and fewer active sites are generated on thesurface after sulphurization.

The Applicant's research has thus led to the preparation ofhydrogenation catalysts from molybdenum and optionally at least oneelement from group VIII, in particular nickel, by modifying the chemicaland structural composition of the metallic species, precursors of theactive phases, in order to modify the interactions between the supportand these precursors in order to better sulphurize the tungsten, whichis recognized as being difficult to sulphurize, but also in order tomodify the interactions between the support and the active sulphidephase of the catalyst in order to disperse it better. In particular, theApplicant's work has led to the use of mononuclear precursors based onmolybdenum in their monomeric or dimeric form having at least one Mo═Oor Mo—OR bond or at least one Mo═S or Mo—SR bond where [R═C_(x)H_(y)where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR′)₃ or R═Si(R′)₃ whereR′═C_(x′)H_(y′) where x′≧1 and (x′−1)≦y′≦(2x′+1)], as particularprecursors of the active phase of the catalysts used in hydrogenationreactions in hydrotreatment processes and processes for thehydrocracking of hydrocarbon feeds in accordance with the invention.

The Applicant has thus demonstrated that a supported catalyst preparedfrom at least one mononuclear precursor based on Mo in its monomeric ordimeric form and having at least one

Mo═O or Mo—OR bond or at least one Mo═S or Mo—SR bond where[R═C_(x)H_(y) where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR′)₃ or R═Si(R′)₃where R′═C_(x′)H_(y′) where x′≧1 and (x′−1)≦y′≦(2x′+1)], in accordancewith a particular mode of preparation, exhibits improved sulphurizationand improved catalytic activity compared with catalysts prepared fromstandard precursors such as polyoxometallates, said catalyst havingadvantageously been pre-sulphurized then used in a hydrotreatment orhydrocracking process.

DESCRIPTION OF THE INVENTION Aims of the Invention

The invention concerns a process for the preparation of a supportedcatalyst starting from at least one mononuclear precursor based onmolybdenum in its monomeric or dimeric form, having at least one Mo═O orMo—OR bond or at least one Mo═S or Mo—SR bond where [R═C_(x)H_(y) wherex≧1 and (x−1)≦y≦(2x+1) or R═Si(OR′)₃ or R═Si(R′)₃ where R′═C_(x′)H_(y′)where x′≧1 and (x′−1)≦y′≦(2x′+1)], and optionally at least one elementfrom group VIII.

The invention also concerns the catalyst that can be prepared by saidpreparation process.

Finally, the invention concerns the use of said catalyst which can beprepared in this manner in hydrogenation reactions, in particular inhydrotreatment and hydrocracking processes.

SUMMARY OF THE INVENTION

The invention concerns a process for the preparation of a catalystcomprising at least one support, optionally at least one metal fromgroup VIII of the periodic classification of the elements and at leastmolybdenum, in which:

-   -   the molybdenum is introduced onto the support, in an organic        solvent A, in the form of at least one mononuclear precursor        compound based on Mo, in its monomeric or dimeric form, having        at least one Mo═O or Mo—OR bond or at least one Mo═S or Mo—SR        bond where [R═C_(x)H_(y) where x≧1 and (x−1)≦y≦(2x+1) or        R═Si(OR′)₃ or R═Si(R′)₃ where R′═C_(x′)H_(y′) where x′≧1 and        (x′−1)≦y′≦(2x′+1)],    -   and a heat treatment of the thus-impregnated support is carried        out by drying at a temperature of less than 200° C.

Said drying may be carried out in an anhydrous atmosphere or under lowvacuum or high vacuum or in a stream of inert gas.

Preferably, said drying is carried out under vacuum and at ambienttemperature.

The metal from group VIII is advantageously selected from cobalt, ironand nickel.

The metal from group VIII is preferably nickel.

The molybdenum precursor is advantageously a mononuclear precursor basedon Mo, used in its monomeric or dimeric form, with formula

Mo(═O)_(n)(═S)_(n′)(OR)_(a)(SR′)_(b)(L1)_(c)(L2)_(d)(L3)_(e)(L4)_(f)(L5)_(g)

where R═C_(x)H_(y), where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR″)₃ orR═Si(R″)₃ where R″═C_(x′)′H_(y′)′ where [x″≧1 and (x″−1)≦y″≦(2x″+1)],where R′═C_(x′)H_(y′) where x′≧1 and (x′−1)≦y′≦(2x′+1) or R′═Si(OR′″)₃or R′═Si(R′″)₃where R′″═C_(x′″)H_(y′″) where [x′″≧1 and (x′″−1)≦y′″≦(2x′″+1)],where 0≦n+n′≦2 and 0≦n≦2 and 0≦n′≦2,where, if n=n′=0, then (a≠0 or b≠0) and [(a+b+c+d+e+f+g=6 and 0≦a≦6,0≦b≦6, 0≦c≦6, 0≦d≦6, 0≦e≦6, 0≦f≦6, 0≦g≦6, or (a+b+c+d+e+f+g=5 and 0≦a≦5,0≦b≦5, 0≦c≦5, 0≦d≦5, 0≦e≦5, 0≦f≦5, 0≦g≦5), or (a+b+c+d+e+f+g=4 and0≦a≦4, 0≦b≦4, 0≦c≦4, 0≦d≦4, 0≦e≦4, 0≦f≦4, 0≦g≦4)],where, if [(n=1 and n′=0) or (n′=1 and n=0)], then [a+b+c+d+e+f+g=4 and0≦a≦4, 0≦b≦4, 0≦c≦4, 0≦d≦4, 0≦e≦4, 0≦f≦4, 0≦g≦4)] or [(a+b+c+d+e+f+g=3and 0≦a≦3, 0≦b≦3, 0≦c≦3, 0≦d≦3, 0≦e≦3, 0≦f≦3, 0≦g≦3)],where, if [n+n′=2 and 0≦n≦2 and 0≦n′≦2], then (a+b+c+d+e+f+g=2 and0≦a≦2, 0≦b≦2, 0≦c≦2, 0≦d≦2, 0≦e≦2, 0≦f≦2, 0≦g≦2),with (L1), (L2), (L3), (L4) and (L5) being selected from ligands of thetype THF, dimethyl ether, dimethylsulphide, P(CH₃)₃, allyl, aryl,halogen, amine, acetate, acetylacetonate, halide, hydroxide, —SH or anyother ligand known to the skilled person.

Preferably, the molybdenum precursor is selected from Mo(OEt)₅,Mo(OEt)₆, Mo(═O)(OEt)₄, Mo(═S)(OEt)₄, Mo(═S)(SEt)₄, Mo(═O)₂(OEt)₂,Mo(OC₆H₅)₆, Mo(SEt)₅, Mo(SEt)₆, Mo(OEt)(SEt)₄, Mo(OEt)₂(SEt)₃,Mo(OEt)₃(SEt)₂, Mo(OEt)₄(SEt), Mo(═O)(OEt)₃(acac) with Et═CH₂CH₃ (ethylgroup) and acac=(CH₃COCHCOCH₃)⁻ (acetylacetonate) in their monomeric ordimeric form.

The molybdenum and the optional metal or metals from group VIII may beintroduced simultaneously or successively.

Advantageously, the preparation process comprises at least one finalstep for gas phase sulphurization carried out in situ and/or ex situ.

-   -   More particularly, the preparation process may comprise at least        the following steps:        -   a) impregnation by bringing a solution S comprising the            organic solvent A and at least said mononuclear precursor            based on molybdenum, in its monomeric or dimeric form,            having at least one Mo═O or Mo—OR bond or at least one Mo═S            or Mo—SR bond where [R═C_(x)H_(y) where x≧1 and            (x−1)≦y≦(2x+1) or R═Si(OR′)₃ or R═Si(R′)₃ where            R′═C_(x′)H_(y′) where x′≧1 and (x′−1)≦y′≦(2x′+1)], into            contact with a porous mineral support, which has been            calcined under low vacuum or high vacuum or in a stream of            inert gas;        -   b) maturing in an anhydrous atmosphere;        -   c) drying the impregnated support at a temperature of less            than 200° C. in an anhydrous atmosphere or under low vacuum            or high vacuum or in a stream of inert gas;        -   d) ex situ sulphurization in a H₂S/H₂ or H₂S/N₂ mixture            containing at least 5% by volume of H₂S in the mixture at a            temperature equal to or higher than ambient temperature.

The optional metal from group VIII may be introduced into step a) in thesame solution S as the molybdenum precursor or after the drying c) in apost-impregnation step a2) with the aid of a solution using an organicsolvent B, or after the sulphurization step d) in a post-impregnationstep a3) with the aid of an aqueous or organic solution.

The invention also concerns a catalyst which is susceptible of beingprepared in accordance with said process.

Preferably, said catalyst comprises a molybdenum content in the range 4%to 30% by weight and a metal or metals from group VIII content in therange 0.1% to 8% by weight with respect to the total catalyst weight.

The invention also concerns the use of said catalyst in reactions forthe hydrogenation of hydrocarbon feeds, preferably for hydrotreatment orhydrocracking.

DETAILED DESCRIPTION OF THE INVENTION

The invention concerns a process for the preparation of a catalyst forcarrying out hydrogenation reactions in hydrotreatment and hydrocrackingprocesses, prepared from at least one mononuclear precursor based onmolybdenum, in its monomeric or dimeric form, having at least one Mo═Oor Mo—OR bond or at least one Mo═S or Mo—SR bond where [R═C_(x)H_(y)where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR′)₃ or R═Si(R′)₃ whereR′═C_(x′)H_(y′) where x′≧1 and (x′−1)≦y′≦(2x′+1)], and optionally atleast one element from group VIII. Said precursors are deposited, usingany method known to the skilled person, onto an oxide support suitablefor the process in which it is used, said catalyst being dried at atemperature of less than 200° C. and advantageously being sulphurizedbefore being deployed in said process.

One of the advantages of the present invention thus resides in aninnovative preparation of hydrotreatment catalysts based on molybdenumwhich allows for better dispersion by grafting and preservation of theprecursors onto the support surface, even onto a silica support. Theseimprovements mean that potentially, more active phase of the sulphidetype can be generated, and thus potentially, more active sites can begenerated for carrying out the desired hydrogenation or hydrocrackingreactions and thus higher activities for the catalysts of the inventioncan be generated compared with those encountered in the literature, oractivities can be generated which are identical to conventionalcatalysts but with half the number of metal atoms on the catalyst.

Preferably, said preparation process comprises at least the followingsteps:

-   -   a) a step for impregnation by bringing a solution comprising an        organic solvent A and at least one mononuclear precursor based        on Mo, in its monomeric or dimeric form, having at least one        Mo═O or Mo—OR bond or at least one Mo═S or Mo—SR bond where        [R═C_(x)H_(y) where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR′)₃ or        R═Si(R′)₃ where R′ ═C_(x′)H_(y′) where x′≧1 and        (x′−1)≦y′≦(2x′+1)], into contact with a porous mineral support,        which has advantageously been calcined under low vacuum or high        vacuum or in a stream of inert gas to evacuate the water which        might be physisorbed on said support;    -   b) a maturation step;    -   c) a step for drying the impregnated support at a temperature of        less than 200° C., in an anhydrous atmosphere or under low        vacuum or high vacuum or in a stream of inert gas;    -   d) a step for sulphurization, preferably carried out ex situ in        a H₂S/H₂ or H₂S/N₂ mixture containing at least 5% by volume of        H₂S in the mixture at a temperature equal to or higher than        ambient temperature.

The optional element or elements from group VIII, hereinafter denotedthe promoter(s), may be introduced in solution either:

-   -   i) at the impregnation step a), co-impregnated with the        mononuclear precursor based on molybdenum;    -   ii) after the drying step c) in a step known as        post-impregnation a2) with the aid of a solution using an        organic solvent B. In this case, a second step for maturation        b2) and a second drying step c2) at a temperature of less than        200° C. are necessary and may be carried out under the same        conditions as the conditions described during steps b) and c);    -   iii) after step d), in a post-impregnation step a3) with the aid        of an aqueous solution or an organic solution. In this case, it        is necessary to add a new maturation step b3), a new drying step        c3) at a temperature of less than 200° C. and a new        sulphurization step d2) before using the catalyst in the        hydrotreatment or hydrocracking process in accordance with the        invention.

The mononuclear precursor based on Mo, used in its monomeric or dimericform, in accordance with the invention advantageously has the formula:

Mo(═O)_(n)(═S)_(n′)(OR)_(a)(SR′)_(b)(L1)_(c)(L2)_(d)(L3)_(e)(L4)_(f)(L5)_(g)

where R═C_(x)H_(y) where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR″)₃ orR═Si(R″)₃ where R″═C_(x′)′H_(y′)′ where [x″≧1 and (x″−1)≦y″≦(2x″-+1)],where R′═C_(x′)H_(y′) where x′≧1 and (x′−1)≦y′≦(2x′+1) or R′═Si(OR′″)₃or R′═Si(R′″)₃where R′″═C_(x′″)H_(y′″) where [x′″≧1 and (x′″−1)≦y′″≦(2x′″+)],where 0≦n+n′≦2 and 0≦n≦2 and 0≦n′≦2,where, if n=n′=0, then (a≠0 or b≠0) and [(a+b+c+d+e+f+g=6 and 0≦a≦6,0≦b≦6, 0≦c≦6, 0≦d≦6, 0≦e≦6, 0≦f≦6, 0≦g≦6, or (a+b+c+d+e+f+g=5 and 0≦a≦5,0≦b≦5, 0≦c≦5, 0≦d≦5, 0≦e≦5, 0≦f≦5, 0≦g≦5), or (a+b+c+d+e+f+g=4 and0≦a≦4, 0≦b≦4, 0≦c≦4, 0≦d≦4, 0≦e≦4, 0≦f≦4, 0≦g≦4)],where, if [(n=1 and n′=0) or (n′=1 and n=0)], then [a+b+c+d+e+f+g=4 and0≦a≦4, 0≦b≦4, 0≦c≦4, 0≦d≦4, 0≦e≦4, 0≦f≦4, 0≦g≦4)] or [(a+b+c+d+e+f+g=3and 0≦a≦3, 0≦b≦3, 0≦c≦3, 0≦d≦3, 0≦e≦3, 0≦f≦3, 0≦g≦3)],where, if [n+n′=2 and 0≦n≦2 and 0≦n′≦2], then (a+b+c+d+e+f+g=2 and0≦a≦2, 0≦b≦2, 0≦c≦2, 0≦d≦2, 0≦e≦2, 0≦f≦2, 0≦g≦2),with (L1), (L2), (L3), (L4) and (L5) being ligands which are well knownto the skilled person and of type THF, dimethyl ether, dimethylsulphide,P(CH₃)₃, allyl, aryl, halogenated (selected from fluorinated,chlorinated and brominated), amine, acetate, acetylacetonate, halide,hydroxide, —SH, etc. Preferably, the ligands are selected fromacetylacetonate, THF and dimethyl ether.

Preferably, the precursors in accordance with the invention do notcontain the ligand (L1), (L2), (L3), (L4) and (L5).

Preferably, the precursors in accordance with the invention are selectedfrom the following compounds: Mo(OEt)₅, Mo(OEt)₆, Mo(═O)(OEt)₄,Mo(═S)(OEt)₄, Mo(═S)(SEt)₄, Mo(═O)₂(OEt)₂, Mo(OC₆H₅)₆, Mo(SEt)₅,Mo(SEt)₆, Mo(OEt)(SEt)₄, Mo(OEt)₂(SEt)₃, Mo(OEt)₃(SEt)₂, Mo(OEt)₄(SEt),Mo(═O)(OEt)₃(acac) with Et=CH₂CH₃ (ethyl group) and acac=(CH₃COCHCOCH₃)⁻(acetylacetonate), in their monomeric or dimeric form.

Still more preferably, the precursor in accordance with the invention isMo(OEt)₅.

The quantity of molybdenum, Mo, is generally in the range 4% to 30% byweight with respect to the final catalyst, and preferably in the range7% to 25% by weight with respect to the final catalyst, obtained afterthe last preparation step, before deploying it in the hydrotreatmentprocess or the hydrocracking process.

The surface density, which corresponds to the quantity of molybdenumatoms, Mo, deposited per unit surface area of the support, isadvantageously in the range 0.5 to 8 atoms of Mo per square nanometre ofsupport, preferably in the range 1 to 7 Mo atoms per square nanometre ofsupport.

Step a), for bringing the solution and the support into contact, is animpregnation. Impregnations are well known to the skilled person. Theimpregnation method of the invention is selected from dry impregnation,excess impregnation, and successive impregnations. The method termed dryimpregnation is advantageously used.

The organic solvent A used in step a) is generally an alkane, analcohol, an ether, a ketone, a chlorinated solvent or an aromaticcompound. Cyclohexane and n-hexane are preferably used.

Step b) is a maturation step intended to allow the species to diffuse tothe core of the support. It is advantageously carried out in ananhydrous atmosphere (without water), preferably for 30 minutes to 24hours at ambient temperature. The atmosphere should preferably beanhydrous so as not to polycondense the pre-impregnated precursors.

Drying carried out during step c) is intended to remove the impregnationsolvent A. The atmosphere should preferably be anhydrous (no water) sothat said pre-impregnated precursors are not polycondensed. Thetemperature must not exceed 200° C. in order to keep said precursorsgrafted or deposited on the surface of the support intact. Preferably,the temperature will not exceed 120° C. Highly preferably, drying iscarried out under vacuum at ambient temperature. This step canalternatively be carried out by passing through an inert gas.

Sulphurization step d) is advantageously carried out ex situ using aH₂S/H₂ or H₂S/N₂ gas mixture containing at least 5% by volume of H₂S inthe mixture at a temperature which is ambient temperature or higher, ata total pressure equal to or higher than 1 bar for at least 2 h.Preferably, the sulphurization temperature is 250° C. Highly preferably,the sulphurization temperature is 350° C.

Sulphurization step d) may also, or in addition to step d) carried outex situ, be carried out in situ at the start of carrying out thecatalytic process using the catalyst, for example a hydrotreatment orhydrocracking process, using any sulphurization process which is wellknown to the skilled person, as described above.

The preferred elements from group VIII are non-noble elements: they areselected from Ni, Co and Fe. Preferably, the elements from group VIIIare cobalt and nickel. Highly preferably, the element from group VIII isnickel. The metal from group VIII is introduced in the form of salts,chelating compounds, alkoxides or glycoxides, and preferably in the formof acetylacetonate or acetate.

If the promoter is introduced as described in the invention in i) andii), the compounds containing the element from group VIII are preferablysulphur-containing compounds, oxygen-containing compounds, chelatingcompounds, alkoxides and glycoxides. Preferably, it is introduced in theform of acetylacetonate or acetate.

If the promoter is introduced as described in the invention at iii), thecompounds containing the element from group VIII may be introduced inthe form of salts, sulphur-containing compounds, oxygen-containingcompounds, chelating compounds, alkoxides and glycoxides. Preferably, itis introduced in the form of acetylacetonate or acetate.

The sources of elements from group VIII which may advantageously be usedin the form of salts are well known to the skilled person. They areselected from nitrates, sulphates, hydroxides, phosphates and halidesselected from chlorides, bromides and fluorides.

The promoter elements from group VIII are advantageously present in thecatalyst in quantities in the range 0.1% to 8% by weight, preferably inthe range 0.5% to 5% by weight with respect to the final catalystobtained after the last preparation step, before using it in thehydrotreatment process or the hydrocracking process.

The organic solvent B used when the promoter is introduced after step c)in a step termed post-impregnation is generally an alkane, an alcohol,an ether, a ketone, a chlorinated compound or an aromatic compound.Toluene, benzene, dichloromethane, tetrahydrofuran, cyclohexane,n-hexane, ethanol, methanol and acetone are preferably used.

The solvent used for impregnation of the promoter (element from groupVIII) in the case of step iii) corresponds either to the organic solventB in the case in which non-saline precursors and water are used, or analcohol when the precursors are saline.

The hydrodehydrogenating function of said catalytic precursor is ensuredby molybdenum and optionally by at least one element from group VIII.Advantageously, the hydrodehydrogenating function is selected from thegroup formed by combinations of the elements: nickel-molybdenum orcobalt-molybdenum or nickel-cobalt-molybdenum.The support for the catalyst of the invention is a porous mineralsupport which advantageously comprises at least aluminium and/or atleast silicon.

Preferably, said support comprises at least one aluminium oxide or atleast one silicon oxide. Advantageously, said support may or may not beacidic. Advantageously, said support may or may not be mesostructured.

Said porous mineral support may advantageously be selected fromtransition aluminas, doped aluminas, preferably with phosphorus, boronand/or fluorine, silicalite and silicas, aluminosilicates, preferablyamorphous or of low crystallinity, crystallized non-zeolitic molecularsieves such as silicoaluminophosphates, aluminophosphates,ferrosilicates, titanium silicoaluminates, borosilicates,chromosilicates and transition metal aluminophosphates, alone or as amixture.

In the case in which said porous mineral support is selected fromtransition aluminas, silicalite and silicas such as mesoporous silicas,for example, said support is not acidic. The term “transition alumina”means, for example, an alpha phase alumina, a delta phase alumina, agamma phase alumina or a mixture of aluminas from these various phases.

In the case in which said porous mineral support is selected fromaluminosilicates, preferably amorphous or of low crystallinity,non-zeolitic crystalline molecular sieves such assilicoaluminophosphates, aluminophosphates, ferrosilicates, titaniumsilicoaluminates, borosilicates, chromosilicates and transition metalaluminophosphates, doped aluminas, preferably with phosphorus, boronand/or fluorine, said support is acidic. Any known silica-alumina or anyaluminosilicate known to the skilled person is suitable in the contextof the invention.

When said porous mineral support is said to be mesostructured, it thencomprises elementary particles organized on the mesopore scale of thematerial of the invention, i.e. an organized porosity on the scale ofpores with a uniform diameter in the range 1.5 to 50 nm, preferably inthe range 1.5 to 30 nm and still more preferably in the range 4 to 20 nmand distributed in a homogeneous and regular manner in each of saidparticles (mesostructuring). The material located between the mesoporesof the elementary mesostructured particle is amorphous and forms wallsor partitions the thickness of which is in the range 1 to 30 nm,preferably in the range 1 to 10 nm. The thickness of the wallscorresponds to the distance separating a first mesopore from a secondmesopore, the second mesopore being the pore closest to said firstmesopore. The organization of the mesoporosity described above leads toa structure of said constituent particle of said support, which may behexagonal, vermicular or cubic, preferably hexagonal. Preferably, saidmesostructured porous mineral support is selected from silica andsilica-alumina.

In addition to at least one of the oxide compounds cited above, theporous mineral support of the invention, whether or not it is acidic,mesostructured or not mesostructured, may also advantageously compriseat least one zeolite and in particular but not restricted to thoselisted in the “Atlas of Zeolite Framework types”, 6^(th) revisededition, 2007, Ch. Baerlocher, L. B. L. McCusker, D. H. Olson”. Thezeolitic crystals may be selected from the zeolites IZM-2, ZSM-5,ZSM-12, ZSM-48, ZSM-22, ZSM-23, ZBM-30, EU-2, EU-11, Silicalite, Beta,zeolite A, Faujasite, Y, USY, VUSY, SDUSY, Mordenite, NU-10, NU-87,NU-88, NU-86, NU-85, IM-5, IM-12, IM-16, Ferrierite and EU-1. Highlypreferably, the zeolitic crystals may be selected from zeolites withstructure type MFI, BEA, FAU, and LTA. Different zeolitic crystals andin particular zeolites with a different structure type may be present inthe porous mineral support constituting the material in accordance withthe invention. In particular, the porous mineral support in accordancewith the invention may advantageously comprise at least first zeoliticcrystals the zeolite of which is selected from the zeolites IZM-2,ZSM-5, ZSM-12, ZSM-48, ZSM-22, ZSM-23, ZBM-30, EU-2, EU-11, Silicalite,Beta, zeolite A, Faujasite, Y, USY, VUSY, SDUSY, Mordenite, NU-10,NU-87, NU-88, NU-86, NU-85, IM-5, IM-12, IM-16, Ferrierite and EU-1,preferably from zeolites with structure type MFI, BEA, FAU, and LTA andat least second zeolitic crystals the zeolite of which is different fromthe first zeolitic crystals and is selected from the zeolites IZM-2,ZSM-5, ZSM-12, ZSM-48, ZSM-22, ZSM-23, ZBM-30, EU-2, EU-11, Silicalite,Beta, zeolite A, Faujasite, Y, USY, VUSY, SDUSY, Mordenite, NU-10,NU-87, NU-88, NU-86, NU-85, IM-5, IM-12, IM-16, Ferrierite and EU-1,preferably from zeolites with structure type MFI, BEA, FAU, and LTA. Thezeolitic crystals advantageously comprise at least one zeolite which iseither entirely silicic or, in addition to silicon, contains at leastone element T selected from aluminium, iron, boron, indium, gallium andgermanium, preferably aluminium.

In addition to at least one of the oxide compounds cited above, theporous mineral support may also advantageously comprise at least onesimple synthetic or natural clay of the dioctahedral 2:1 phyllosilicateor trioctahedral 3:1 phyllosilicate type such as kaolinite, antigorite,chrysotile, montmorillonnite, beidellite, vermiculite, talc, hectorite,saponite or laponite. These clays may also optionally have beendelaminated.

Preferably, said porous mineral support is selected from mesoporousalumina and silica-alumina used alone or as a mixture, or mesostructuredsilicas and silica-aluminas, used alone or as a mixture.

The catalyst may be used in any of the forms known to the skilledperson: it may be in the form of a powder, in the form of beads or inthe form of cylindrical, trilobal or quadrilobal extrudates. Differentshapes may be mixed.

In accordance with the invention, said catalyst is advantageouslypartially sulphurized by means of at least one step for sulphurizationin the gas phase described in step d) of the preparation process, beforebeing used in the hydrotreatment or hydrocracking process of theinvention. This sulphurization step described in step d) generates theactive sulphide phase in a partial manner, but it can be used to preventleaching of the metallic precursors in contact with the hydrocarbon feedto be treated or possibly in contact with the sulphurization feed. Thecatalyst obtained is used in a hydrotreatment or hydrocracking unitwhere it can undergo in situ sulphurization carried out with the aid ofthe feed to be treated in the presence of hydrogen and hydrogen sulphide(H₂S) introduced as is or obtained from the decomposition of an organicsulphur-containing compound selected from dimethyldisulphide (DMDS),dimethylsulphide, n-butylmercaptan and polysulphide compounds. Thissulphurization is carried out at a temperature in the range 200° C. to600° C., preferably in the range 300° C. to 400° C., using processeswhich are well known to the skilled person.

The Hydrotreatment and Hydrocracking Processes, as Well as Feeds

Finally, the invention also concerns the use of the catalyst of theinvention in processes for the hydrotreatment and hydrocracking of oilcuts.

The catalyst prepared with the process of the invention mayadvantageously be used in any process known to the skilled personnecessitating hydrogenation reactions of hydrocarbon cuts and preferablyof catalytically cracked gasoline cuts. The hydrotreatment andhydrocracking processes of the invention may advantageously be carriedout in any type of reactor operated in fixed bed or moving bed orebullated bed mode. Preferably, said hydrotreatment process or saidhydrocracking process is carried out in a reactor operated in fixed bedmode.

The catalysts obtained by the preparation process of the invention areadvantageously used for reactions for the hydrotreatment of hydrocarbonfeeds such as oil cuts, cuts obtained from coal or hydrocarbons producedfrom natural gas, more particularly necessitating hydrogenationreactions: the hydrogenation of aromatics, hydrodenitrogenation,hydrodesulphurization, hydrodemetallization or hydrocracking ofhydrocarbon feeds are reactions which may be cited.

These catalysts may also advantageously be used during pre-treatment ofcatalytically cracked feeds or feeds for the hydrodesulphurization ofresidues or for the intense hydrodesulphurization of gas oils (ULSD orUltra Low Sulphur Diesel).

Examples of feeds employed in the hydrotreatment processes aregasolines, gas oils, vacuum gas oils, atmospheric residues, vacuumresidues, atmospheric distillates, vacuum distillates, heavy fuels,oils, waxes and paraffins, spent oils, residues or deasphalted crudes,or feeds deriving from thermal or catalytic conversion processes, usedalone or as mixtures. The feeds which are treated, in particular thosecited above, generally contain heteroatoms such as sulphur, oxygen andnitrogen and, for the heavy feeds, they usually also contain metals.

The operating conditions used in the processes using the reactions forthe hydrotreatment of hydrocarbon feeds described above are generally asfollows: the temperature is advantageously in the range 180° C. to 450°C., preferably in the range 250° C. to 440° C., the pressure isadvantageously in the range 0.5 to 30 MPa, preferably in the range 1 to18 MPa, the hourly space velocity is advantageously in the range 0.1 to20 h⁻¹, preferably in the range 0.2 to 5 h⁻¹, and the hydrogen/feedratio, expressed as the volume of hydrogen measured under normaltemperature and pressure conditions per volume of liquid feed, isadvantageously in the range 50 L/L to 2000 L/L.

Examples of the feeds employed in the hydrocracking reactions are LCO(light cycle oil (light gas oils obtained from a catalytic crackingunit)), atmospheric distillates, vacuum distillates, for example gasoils obtained from straight run distillation of crude or conversionunits such as FCC, coking or visbreaking units, feeds deriving fromaromatics extraction units, lubricating base oils or bases obtained fromsolvent dewaxing of lubricating base oils, distillates deriving fromfixed bed or ebullated bed desulphurization or hydroconversionprocesses, atmospheric residues and/or vacuum residues and/ordeasphalted oils, or the feed may be a deasphalted oil or comprisevegetable oils, or indeed derive from the conversion of feeds obtainedfrom biomass. Said hydrocarbon feed treated in the hydrocracking processof the invention may also be a mixture of said feeds as cited above. Thehydrocarbon feeds present in said feed are aromatic compounds, olefiniccompounds, naphthenic compounds and/or paraffinic compounds.

Said hydrocarbon feed advantageously comprises heteroatoms. Preferably,said heteroatoms are selected from nitrogen, sulphur and a mixture ofthese two elements. When nitrogen is present in said feed to be treated,the nitrogen content is 500 ppm or more, and preferably it is in therange 500 to 10000 ppm by weight, more preferably in the range 700 to4000 ppm by weight and still more preferably in the range 1000 to 4000ppm. When sulphur is present in said feed to be treated, the sulphurcontent is in the range 0.01% to 5% by weight, preferably in the range0.2% to 4% by weight and still more preferably in the range 0.5% to 3%by weight.

Said hydrocarbon feed may optionally advantageously contain metals, inparticular nickel and vanadium. The cumulative nickel and vanadiumcontent of said hydrocarbon feed treated using the hydrocracking processof the invention is preferably less than 1 ppm by weight. Theasphaltenes content of said hydrocarbon feed is generally less than 3000ppm, preferably less than 1000 ppm, still more preferably less than 200ppm.

The hydrocracking process of the invention covers the fields of pressureand conversion from mild hydrocracking to high pressure hydrocracking.The term “mild hydrocracking” means hydrocracking leading to moderateconversions, generally less than 40%, and operating at low pressure,generally between 2 MPa and 10 MPa. The hydrocracking process of theinvention is carried out in the presence of at least one hydrotreatmentcatalyst or hydrocracking catalyst in accordance with the invention. Thehydrocracking process of the invention may be carried out in one or twosteps, independently of the pressure at which said process is carriedout. It is carried out in the presence of one or more catalyst(s)obtained using the preparation process described above, in one or morereaction unit(s) equipped with one or more reactors(s).

The operating conditions used in the hydrocracking processes of theinvention may vary widely as a function of the nature of the feed, thequality of the desired products and the facilities available to therefiner. In accordance with the hydrocracking process of the invention,said hydrocracking catalyst is advantageously brought into contact, inthe presence of hydrogen, with said hydrocarbon feed at a temperature ofmore than 200° C., often in the range 250° C. to 480° C., advantageouslyin the range 320° C. to 450° C., preferably in the range 330° C. to 435°C., at a pressure of more than 1 MPa, often in the range 2 to 25 MPa,preferably in the range 3 to 20 MPa, the space velocity (volume flowrate of feed divided by the volume of catalyst) being in the range 0.1to 20 h⁻¹, preferably in the range 0.1 to 6 h⁻¹, still more preferablyin the range 0.2 to 3 h⁻¹, and the quantity of hydrogen introduced issuch that the volume ratio of litres of hydrogen/litres of hydrocarbonis in the range 80 to 5000 L/L, often in the range 100 to 2000 L/L.

These operating conditions used in the hydrocracking process of theinvention can generally be used to reach conversions per pass intoproducts with boiling points of at most 370° C. and advantageously atmost 340° C., of more than 15%, still more preferably in the range 20%to 95%.

EXAMPLES

The examples below are presented by way of illustration; theydemonstrate the large increase in activity of catalysts prepared inaccordance with the process of the invention compared with prior artcatalysts, and specify the invention without in any way limiting itsscope.

Example 1 NiMo Catalyst Supported on Alumina, with a Surface Density of3 Mo/Nm² and Ni/Mo=0.3 (at/at) (in Accordance with the Invention)

The molybdenum was dry impregnated in a strictly non-aqueous medium ontoa commercial γ alumina type support synthesized by calcining a gel ofaluminium salts (287 m²/g). The support was initially calcined at 300°C. in air for 6 hours at atmospheric pressure. It was then heated to300° C. for 14 hours under high vacuum (10⁻⁵ mbar) before being storedin an inert medium, in a glove box. The molybdenum precursor wasmolybdenum pentaethoxide, Mo(OC₂H₅)₅. Dry degassed cyclohexane was usedas the solvent. 1.96 mL of impregnation solution, prepared from 1.18 gof precursor, was impregnated onto 2.58 g of dry support. The quantityof molybdenum was adjusted so as to obtain 3 Mo/nm². After maturing for15 hours, the extrudates were dried under vacuum (10⁻⁵ mbar) for 2 hoursat ambient temperature. This non-sulphurized catalyst was defined by theusual notation Mo/Al₂O₃.

A solution of nickel bis-acetylacetonate Ni(acac)₂ was then impregnatedonto this catalyst. Dry degassed toluene was used as the solvent. Thenickel precursor was first dissolved in hot toluene, then 2.45 mL of asolution containing 0.41 g of precursor was impregnated ontoapproximately 3.76 g of Mo/Al₂O₃. After maturing for 15 hours, theextrudates were dried under vacuum (10⁻⁵ mbar) for 3 hours at ambienttemperature. For this non-sulphurized NiMo/Al₂O₃ catalyst, themolybdenum and nickel contents were respectively 11.60% by weight and2.21% by weight, which corresponded to an actual surface density of 3.0Mo/nm² and a Ni/Mo atomic ratio of 0.30. This catalyst C1 was inaccordance with the invention.

Example 2 NiMo Catalyst Supported on Alumina, with a Surface Density of3 Mo/Nm² and Ni/Mo=0.3 (at/at) (not in Accordance with the Invention)

The molybdenum and nickel were dry co-impregnated in an aqueous mediumonto a commercial γ alumina type support synthesised by calcining a gelof aluminium salts (289 m²/g). The molybdenum precursor was ammoniumheptamolybdate (NH₄)₆Mo₇O₂₄.×H₂O. The nickel precursor was nickelnitrate Ni(NO₃)₂.×H₂O. The quantities of precursors were adjusted so asto obtain 3 Mo/nm² and Ni/Mo=0.30 (at/at). After maturing for 15 hours,the extrudates were dried at 120° C. for 15 hours. They were thencalcined at 450° C. in a stream of air for 2 hours. The molybdenum andnickel contents of this non-sulphurized NiMo/Al₂O₃ catalyst wererespectively 11.75% by weight and 2.12% by weight, which corresponded toan actual surface density of 3.0 Mo/nm² and a Ni/Mo atomic ratio of0.29. This catalyst H1 was not in accordance with the invention.

Example 3 Test for the Hydrogenation of Toluene (Aromatic ModelMolecule) in the Presence of Aniline

The test for the hydrogenation of toluene in the presence of aniline isintended to evaluate the hydrogenating activity of supported or bulksulphurized catalysts in the presence of H₂S and under hydrogenpressure. The isomerization which characterizes the acid function of thecatalyst is inhibited by the presence of aniline, at low temperaturesand/or by the presence of NH₃ (obtained from the decomposition ofaniline) at higher temperatures. The aniline and/or NH₃ will react withthe acidic sites of the support by an acid-base reaction. Thecharacteristic isomerization reactions of the acidity of the supportthen do not exist.

We were careful to carry out the comparison of the catalysts on the samecatalytic test unit in order not to falsify the comparisons by usingdifferent catalytic test tools which could produce out-of-line results.

The catalytic test was carried out in the gas phase in a fixed bedtraversed reactor. The test can be broken down into two distinct phases,sulphurization and the catalytic test. The test was carried out at 60bar.

The catalysts were initially sulphurized ex situ in the gas phase((H₂S/H₂ mixture) in which the quantity of H₂S was 15% by volume) at atemperature of 350° C. for 2 h.

Activation Phase:

The catalysts were subjected to a rise in temperature under test feed ina fixed bed traversed tube reactor of a Flowrence type pilot unit (fromAvantium), the fluids moving from top to bottom. The measurements of thehydrogenating activity were carried out immediately after reaching thetest temperature.

Catalytic Test:

The test feed was composed of dimethyldisulphide (DMDS), toluene,cyclohexane and aniline.

The stabilized catalytic activities of equal volumes of catalysts (450μL) were measured at a temperature of 350° C.

The operating conditions of the test were as follows (assuming totalvaporization and the perfect gas law):

For Ptot=60 bar and T=350° C.: PpH₂=36.62 bar PpNH₃=0.09 bar PpH₂S=2.16bar Pptoluene=3.75 bar Ppcyclohexane=15.22 bar

HSV=4 L/L/h during the activation phase, and HSV=2 L/L/h and H₂/feed=450L/L during the test phase.

Effluent samples were analysed by gas chromatography. The catalyticperformances of the catalysts are expressed using the correspondinghydrogenating activity, using first order kinetics:

${AH}_{1.{order}} = {\ln \frac{100}{\left( {100 - {\% \; {HYD}_{toluene}}} \right)}}$

% HYD_(toluene) corresponds to the percentage of hydrogenated toluene.

The catalytic performances are shown in Table 1.

TABLE 1 Relative hydrogenating activity of catalysts C1 and H1. Thesewere expressed as the relative activity, assuming that of catalyst H1was equal to 100. Hydrogenating activity Catalyst relative to H1 C1 (inaccordance with the invention) 145 H1 (not in accordance with theinvention) 100

Table 1 shows the large gain in hydrogenating power obtained for thecatalyst claimed in accordance with the invention prepared on alumina(C1). Catalyst C1, prepared from the molybdenum precursor Mo(OEt)₅ inaccordance with the invention, is more active in hydrogenation than thecatalyst which is homologous in formulation but prepared by aconventional pathway using a heteropolyanion salt (H1).

The entire disclosures of all applications, patents and publications,cited herein and of corresponding French Application No. 13/53940, filedApr. 30, 2013 are incorporated by reference herein.

1. A process for the preparation of a catalyst comprising at least onesupport, optionally at least one metal from group VIII of the periodicclassification of the elements and at least molybdenum, said processbeing characterized in that: the molybdenum is introduced onto thesupport, in an organic solvent A, in the form of at least onemononuclear precursor compound based on Mo, in its monomeric or dimericform, having at least one Mo═O or Mo—OR bond or at least one Mo═S orMo—SR bond where [R═C_(x)H_(y) where x≧1 and (x−1)≦y≦(2x+1) orR═Si(OR′)₃ or R═Si(R′)₃ where R′═C_(x′)H_(y′) where x′≧1 and(x′−1)≦y′≦(2x′+1)], and a heat treatment of the thus-impregnated supportis carried out by drying at a temperature of less than 200° C.
 2. Thepreparation process as claimed in claim 1, in which said drying iscarried out in an anhydrous atmosphere or under low vacuum or highvacuum or in a stream of inert gas.
 3. The process as claimed in claim2, in which said drying is carried out under vacuum and at ambienttemperature.
 4. The process as claimed in claim 1, in which the metalfrom group VIII is selected from cobalt, iron and nickel.
 5. The processas claimed in claim 4, in which the metal from group VIII is nickel. 6.The process as claimed in claim 1, in which the molybdenum precursor isa mononuclear precursor based on Mo, used in its monomeric or dimericform, with formulaMo(═O)_(n)(═S)_(n′)(OR)_(a)(SR′)_(b)(L1)_(c)(L2)_(d)(L3)_(e)(L4)_(f)(L5)_(g)where R═C_(x)H_(y) where x≧1 and (x−1)≦y≦(2x+1) or R═Si(OR″)₃ orR═Si(R″)₃ where R″═C_(x′)′H_(y′)′ where [x″≧1 and (x″−1)≦y″≦(2x″+1)],where R′═C_(x′)H_(y′) where x′≧1 and (x′−1)≦y′≦(2x′+1) or R′═Si(OR′″)₃or R′═Si(R′″)₃ where R′″═C_(x′″)H_(y′″) where [x′″≧1 and(x′″−1)≦y′″≦(2x′″+1)], where 0≦n+n′≦2 and 0≦n≦2 and 0≦n′≦2, where, ifn=n′=0, then (a≠0 or b≠0) and [(a+b+c+d+e+f+g=6 and 0≦a≦6, 0≦b≦6, 0≦c≦6,0≦d≦6, 0≦e≦6, 0≦f≦6, 0≦g≦6, or (a+b+c+d+e+f+g=5 and 0≦a≦5, 0≦b≦5, 0≦c≦5,0≦d≦5, 0≦e≦5, 0≦f≦5, 0≦g≦5), or (a+b+c+d+e+f+g=4 and 0≦a≦4, 0≦b≦4,0≦c≦4, 0≦d≦4, 0≦e≦4, 0≦f≦4, 0≦g≦4)], where, if [(n=1 and n′=0) or (n′=1and n=0)], then [a+b+c+d+e+f+g=4 and 0≦a≦4, 0≦b≦4, 0≦c≦4, 0≦d≦4, 0≦e≦4,0≦f≦4, 0≦g≦4)] or [(a+b+c+d+e+f+g=3 and 0≦a≦3, 0≦b≦3, 0≦c≦3, 0≦d≦3,0≦e≦3, 0≦f≦3, 0≦g≦3)], where, if [n+n′=2 and 0≦n≦2 and 0≦n′≦2], then(a+b+c+d+e+f+g=2 and 0≦a≦2, 0≦b≦2, 0≦c≦2, 0≦d≦2, 0≦e≦2, 0≦f≦2, 0≦g≦2),with (L1), (L2), (L3), (L4) and (L5) being selected from ligands of thetype THF, dimethyl ether, dimethylsulphide, P(CH₃)₃, allyl, aryl,halogen, amine, acetate, acetylacetonate, halide, hydroxide and —SH. 7.The process as claimed in claim 6, in which the molybdenum precursor isselected from Mo(OEt)₅, Mo(OEt)₆, Mo(═O)(OEt)₄, Mo(═S)(OEt)₄,Mo(═S)(SEt)₄, Mo(═O)₂(OEt)₂, Mo(OC₆H₅)₆, Mo(SEt)₅, Mo(SEt)₆,Mo(OEt)(SEt)₄, Mo(OEt)₂(SEt)₃, Mo(OEt)₃(SEt)₂, Mo(OEt)₄(SEt),Mo(═O)(OEt)₃(acac) with Et═CH₂CH₃ (ethyl group) and acac=(CH₃COCHCOCH₃)⁻(acetylacetonate) in their monomeric or dimeric form.
 8. A process forthe preparation of a catalyst as claimed in claim 1, in which themolybdenum and the optional metal or metals from group VIII areintroduced simultaneously or successively.
 9. A process for thepreparation of a catalyst as claimed in claim 1, comprising at least onefinal step for gas phase sulphurization, in situ and/or ex situ.
 10. Aprocess for the preparation of a catalyst as claimed in claim 1,comprising at least the following steps: a) impregnation by bringing asolution S comprising the organic solvent A with at least saidmononuclear precursor based on molybdenum, in its monomeric or dimericform, having at least one Mo═O or Mo—OR bond or at least one Mo═S orMo—SR bond where [R═C_(x)H_(y) where x≧1 and (x−1)≦y≦(2x+1) orR═Si(OR′)₃ or R═Si(R′)₃ where R′═C_(x′)H_(y′) where x′≧1 and(x′−1)≦y′≦(2x′+1)], into contact with a porous mineral support, whichhas been calcined under low vacuum or high vacuum or in a stream ofinert gas; b) maturing in an anhydrous atmosphere; c) drying theimpregnated support at a temperature of less than 200° C. in ananhydrous atmosphere or under low vacuum or high vacuum or in a streamof inert gas; d) ex situ sulphurization in a H₂S/H₂ or H₂S/N₂ mixturecontaining at least 5% by volume of H₂S in the mixture at a temperatureequal to or higher than ambient temperature.
 11. A process for thepreparation of a catalyst as claimed in claim 10, in which the optionalmetal from group VIII is introduced into step a) in the same solution Sas the molybdenum precursor or after the drying c) in apost-impregnation step a2) with the aid of a solution using an organicsolvent B, or after the sulphurization step d) in a post-impregnationstep a3) with the aid of an aqueous or organic solution.
 12. A catalystwhich is susceptible of being prepared by the process of claim
 1. 13.The catalyst as claimed in claim 12, comprising a quantity of molybdenumin the range 4% to 30% by weight and a metal or metals from group VIIIcontent in the range 0.1% to 8% by weight with respect to the totalcatalyst weight.
 14. A method comprising employing a catalyst asprepared in claim 1, in a reaction for the hydrogenation of hydrocarbonfeeds.
 15. A method as claimed in claim 14, for hydrotreatment orhydrocracking.